Compressor unloader



Feb. 27,11940.

S. F. EVELYN COMPRESSOR UNLOADER Filed 'March 11, 1938 Steven E' EvelynINVENTOR BYv . ATTORNEY Patented Pena-1,1940,

PATET., OFFICE 2,191,908 oonrnnssoa uNLoADEn Steven F. Evelyn, Holyoke,Worthington Pump and tion, Harrison, N. J.,

luana., assigner to I Machinery Corporaa corporation of Dela-APPlieltion March 1l, 1938. Serialv No. 195,251

1 Claim.

This invention relates to unloaders for compressors and a general objectof the present invention is to provide a simple, practical, and positiveloading and unloading mechanism for air or gas compressors, which willbe positive in action and will unload the compressor upon the cuttingoil? of operating power thereto and will load the compressor upon thecutting in of operating power.

An object of the present invention is to provide in an unloadermechanism for compressors thervmal time delay means which will provideVa time interval between the starting of the compressor and itsloading,thereby allowing the compressor l5 and its operating motor to reach fullspeed before the load torque is imposed.

With these and other objects in view, as may appear from theaccompanying specication. the

invention consists of various features oi construction and combinationof parts,which will be rst described in connection with the accompanyingdrawing, showing a compressor unloader embodying the invention, and thefeatures forming the Y invention will be speciiically pointed out in theclaims.

In the drawing:

Figure 1 is a diagrammatic view showing the Aimproved unloading andloading mechanism in diagram and showing a part of the compressor insection. A Y

'Figure 2 is a longitudinal section through the valve which controls theloading and unloading ofthe compressor and is taken at right angles tothe line 2-2 of Figure 1.*

Referring more particularly to the drawing the improved unloadingmechanism is shown as used in connection with a single cylindercompressor 1I which is unloaded by the holding open of the suction valve2 by the pressure operated mecha- 'nism 3, all of which isstandardconstruction in present day commercial use. However it is to beunderstood that the unloading mechanism may` be used in connection withany type of compressor and any type of unloading means as desiredwithout departing from the spirit of the present inventio the type ofcompressor shown in the drawing is merely as an illustrating example.

The pressure operating mechanism 3 comprises a cylinder 4 in which ismounted a piston 5. The piston 5 acts on the plunger 6 so that whenpressure 4 behind the piston 5 it will force the plunger `6 downwardlyand hold the suction valve 2 open,

ttlng the compressor I to operate in a completely unloaded condition.when the pressure ing ofthe electric magnetic action fluid is admittedto the cylinder 'Y and the spring 26 moves (Ci. 23o-31) is relievedbehind the piston 5 the spring 1 forces the piston 5 and plunger 6outwardly, relieving the pressure on the suction valve 2 and permittingthe compressor to operate in normal loaded condition. f

The compressor I is operatedi by an electric motor 8 which receives itsenergizing power through the power lines L1 and L2. A switch 9 isinterposed in the power line for controlling the energizing anddeenerglzing of the motor 8. 10

The loading and unloading mechanism comprises a control valve structureIll which is connected through suitable piping II with the receiver I2for providing'air or gas under pressure for operating the unloadingmechanism- 3. The 15 valve III comprises the valve housing I4, in which.is mounted the two valves I5 and I6, cooperat ing respectively withvalve seats I'I and I8. The vpressure uid supply pipe II opens into thebore I9 of the valve housing I4 near one -end and outwardly of the valveI5, while the pipe 20 which conducts the operating pressure fluid to thevalve actuating mechanism 3 opens into the bore I9 bet'ween the valvesI5 and I6.

With the valves I5 and I6 in the positions 25 shown in Figure 2 of thedrawing, the portion of the bore I9 between the valves I5 and I6 isopened to atmosphere through the exhaust passage 2I and the pressurefluid bleeds from the valve actuating mechanism pipe 20 and toatmosphere, permitting 'the spring 6 to act for relieving the pressureon the valve strip 2 at which time the compressor is\\operating in aloaded condition. When the valve I6 is seated and the valve I5 is of!its seat the pressure 35 uid passes around the valve I5 through the boreI9 outwardly through the pipe 2li to the valve actuating mechanism 3 andholds this valve open. The valves l5 and I6 are connected for movementin unison by a stem 22 which has a contact disk 40 23 on its outer end.The contact disk 23 is engaged by the button orf knob 24 on the pivotlever 25, The pivot lever 25 is moved by the energizcoil 26, beingattracted by the of the coil into engagement with 45 the core 21 andwhen it is so moved it actuates the stem 22 to 4seat the valve I5 andmove the valve I6 oi its seat. Thus when the coil 26 is energized thecompressor I operates in a loaded condition. When the coil 26 is(le-energized, the 50 lever 26 moves away from the core 21 of the 'coilA the valve I5 oi its seat and the valve I6 on to its'seat, therebyopening receiver pressure to the!y valve actuating mechanism 3 andunloodisthe compressor, Iteis to j 3 back through the 80 be understoodthat in actual practice the lever 2E may be positioned so that it willmove or fall away from the core 2l under its own weight and that theshowing in Figure l of the drawing is t g n. ti,

.l f of a compressor itis always desirable to relieve the motor 8 andthe compressor l of the load torque until both the motor and thecompressor reach full operating speed and to permit of this action,thermal means are provided to cause a time interval delayY hetween theen of the motor d and the loading of the compressor.

It has heretofore been the practice to provide various types of meansfor providing this time interval delay such as dash pots, and othersimilar mechanical devices, but the present invention embraces theprovision of a thermostatic switch in the form of a bimetal contactcarrying member which controls the operation of the valve lo therebyproviding' al simple, inexpensive, readily replaced and accurate timedelay means which is much simpler in construction and cheaper tomanufacture than the time delay means heretofore employed.

The time delay means 3Q includes, a bimetal plate 3l of approved usualconstruction which acts under temperature diierences to move the contact32, carried thereby into engagement with the stationary contact 33' toclose a circuit through the coil 26 which circuit is broken atpredetermined times as hereinafter referred to. The bimetal blade 3l ofthe thermostatic switch 3l is electrically heated by an electric heatingcoil 33l which is in circuit vwith one oi the power lines:

to the motor.

aieaeos supply of operating pressure fluid to the valve ac mechanism 3and permits the loading of the compressor. The lever 25 has an extension4d thereon which, when the lever 25 moves towards the lcore 2l, engagesthe spring member G5 of the switch 3l and operates the switch blade v38, moving it out of engagement with the contact 36 and into engagementwith the contact $6, thus cutting oli the electric circuit through thecoil 33 and maintaining the circuit through the coil 26 to hold thelever 25 and valve` I0 in compressor loading position, the circuitthrough the coil 26 being maintained by the connection tl with thecontact B6. The heating coil 33 cools when the circuit is brokentherethrough, which allows the blade 3l of the thermostatic switch 3B tocool and move out of engagement with the contact 33', thuspositioningthe thermostatic switch for reoperation the next time thecompressor is started.

' While a particular construction of valve l0 and compressor unloadingmechanism is shown in the drawing and hereinbefore described, it is tobe understood that the present invention of utilizing a thermal meansora. thermostatic switch for controlling the loading and unloading ofthe compressor maybe employed in connection with various other practicaltypes of valves and un- ,In operation, when the-compressori is rststarted by the closing of the switch 9, the bimetal bladel of thethermostatic -switch 30 will be cold and consequently the contacts! and33 will be out of engagement. With the closing of the switch 9 thecircuit is through the wire 34,

trcal circuit is then from the power line L1.

through the wire 34, wire 4l through the coil 25, the wire 42, wire 63,contacts 33' and 32, back through the wire B0 to the power line L3.ThusV the coil 26 is energized and acts on the lever 25 to move it intoengagementwith the core 21. '111e movement of the lever 25 actuetes thevalve structure l0 as heretofore described to cut oif thevaround-through the heating coil 33, through the loading systems nowgenerally known to the trade, without departing from the spirit of thepresent invention.

It will be understood that the invention is not to be limited to thespecific construction or arrangement of parts shown but that they may bewidely modified within the invention defined by the claim.

What is claimed is: y

Inacompressor unloading mechanism, the combination, of an air or gascompressor, an electric Y motor for operatingsaid compressor, meanscontrolling energizing of said motor, pressure operated means forunloading said compressor, a valve for controlling the delivery ofoperating pressure to said pressure operated means, electricallyoperated means for ,operating said valve, a thermostatic switch forcontrolling energizing of said electrically operated means, and a switchin circuit with said thermostatic switclzgand said electrically operatedmeans for cutting the thermostatic switch out of the circuit atpredetermined times and the circuit through said electrically operatedmeans, said electrically operated valve operating means including amagnetic coil, a lever actuated by said coil for operating Vsaid valvesaid lever operating said switch upon movement- 'of. the lever underaction of said magnetic coil.

STEVEN F. EVELYN.'

